Ceramic product and method of making same



June 17, 1952 R. P. DUNMIRE 2,601,105

CERAMIC PRODUCT AND METHOD OF MAKING SAME Filed Aug. 16. 1949 RAW MHTER IHLS 1 1 PREPARING AND BLENDING Z HPPHRHTUS CH/IRGE MEHSURING 3 HNO FEEQING flPPHRHTU-S HIGH PRESSURE FORMING PRESS SENDING 0R COLORING DRYER z 6 Patented June 17, 1952 UNITED STATES ATENT OFFICE CERAMIC PRODUCT AND METHOD OF MAKING SAME 6 Claims. 1

This invention relates generally to ceramic products and more particularly to vitrified'products such as roofing tile, quarry tile, and the like.

The production of such tile by methods in use prior to my invention was a slow, tedious and uneconomic-a1 process which involved a great deal of hand labor and the use of much equipment including a steam-generating plant,- extrusion equipment, driers, drier cars, pallets, periodic or timed kilns, kiln furniture, kiln cars, kiln car tops, conveyors and a great amount of industrial car trackage, all requiring considerable maintenance and replacement.

One of the primary purposes of my present invention is to eliminate the employment of all of the aforementioned equipment as now used and use instead a forming die press and a continuous drier and kiln through which the pressed articles are passed on a conveyor.

Another object of my invention is to provide a method which will eliminate the hand labor heretofore required in placing the pieces delivered from the forming die on pallets, loading them onto drying cars, pushing the cars into the drying chamber, transferring the dried pieces to kiln cars or kilns. sealing the kilns if the periodic type is used, and finally unloading said cars or kilns when the firing operation is completed.

In lieu of all of these manual operations which contribute materially to the cost of producing ceramic products, my invention contemplates the automatic handling of the ceramic material from the time the raw clay, shale or similar material enters the first mixer until the finished vitrified product is automatically delivered by a conveyor, thereby eliminating all of the aforesaid hand labor.

A further object of my invention is to very materially reduce the time required for the making of vitrified ceramic, products. The extent and im-, portance of this time reduction will be appreciated from a comparison of the old with the new. In the old or present method, after the pieces are extruded from the forming die and are placed on pallets in the drier, they are required to remain in the drier for at least twenty-four hours at a temperature of 240 F. In accordance with my method, about one or two hours of drying at approximately the same temperature suflices. Furthermore, when transferred from the drier to a firing kiln, the required time for a firing cycle including loading, firing and drawing in such a sealed periodic kiln is about three weeks, and 1n a tunnel kiln at least sixty hours. In accordance with my method, which employs a continuous conveyor kiln, a kiln firing period of only a few hours is all that is necessary. By this time saving, the production of roofing tile and similar products is greatly expedited, and cheapened.

Another purpose of my invention is to produce an article which before drying and firing will be of such density and rigidity as to be self-sustaining and handleable, thereby eliminating the necessity of the use of pallets and eliminating also the major portion of the time heretofore required for drying articles formed by the extrusion process.

Another object of my invention is the provision of a method which will produce vitrified products of uniform character and quality. Heretofore in the firing of such products, the articles have been set or stacked in periodic or tunnel kilns. Such stacking necessarily disposes some of the articles closer to the source of firing heat than others, with the result that some of the articles are frequently over-fired and others underfired, so that non-uniformity in the character and appearance of the completed products are practically unavoidable. With my present novel method, on the other hand, in the employment of which the articles are passed through a tunnel firing kiln at the same height on a traveling conveyor, each article is subjected during its passage through the kiln to the same heat intensity as every other article, whereby a uniformity of product both as to character and appearance is secured to an extent heretofore unobtainable.

Another important object of my invention is the production of vitrified ceramic products of a superior quality. Such superiority resides not merely in the appearance of theproduct resulting from the uniformity of the firing as above noted, but also in structural characteristics which in crease its rupture strength and its crushing strength and also reduce its absorptive capabilities.

Another object is to efiectfa drastic saving in the amount of heat energy ordinarily required to produce the required degree of vitrification.

, Other objects and many of the inherent advantages of my invention should be readily appreciated by those skilled in the art from the following description when considered in connec tion with the accomanying drawings.

Referring to the drawings:

Fig. 1 illustrates schematically the steps followed in carrying out my novel method; and

Fig. 2 is a vitrified ceramic product in the form of a roofing tile produced by my novel method.

Referring now to the drawings more in detail,

the source of the materials forming the constituents of the product is indicated on the drawing by raw materials and designated by reference character I. These materials are those which enter into the composition of the product to be made and usually consist solely or largely of clay or shale and the like, although other ingredients of similar character may be added to produce a product of a selected composition or color.

The raw material or materials should be in a dry or semi-dry state, containing only such moisture as would normally be absorbed from the ambient atmosphere. If the ingredient materials in the raw state contain more moisture than desirable, a preliminary drying may sometimes be necessary, since the best results from my method are obtained when the materials include not more than three percent by weight of moisture and, should they contain more than five percent, resort to a preliminary drying would in most instances be desirable.

The ingredient materials, after being ground and screened, are mixed and thoroughly blended in any suitable mixing apparatus or mill desig-.

nated on the drawings by reference character 2.

and it is at this point or before that the treatment for the reduction of moisture content is applied, if at all.

From the mixing or blending apparatus, the ingredient material is delivered by suitable means to an apparatus designated generally by reference character 3, which automatically separates and measures out from the mass a charge of the material of predetermined size. Each charge is just large enough to form one of the articles being produced.

The measured charge of ceramic material is then advanced into the die of a forming press by which the charge is compacted and caused to assume the desired shape of the finished article. The structural details of the forming press are of no consequence so far as my present invention is concerned, except that the die used in my process has a movable bottom for ejecting the material which is charged between the top and bottom of the die in the press by a charging mechanism when the die top is at the end of its upward stroke. After charging the die with the dry or semi-dry mixture to a predetermined amount the charging mechanism is withdrawn automatically, the die top travels downward and forms the semi-dry material into a desired shape, after which on the upward stroke of the top of the die the bottom of the die rises to a predetermined level or enough so that the charging equipment functions to eject the formed piece onto the apron of the drier section of the continuous kiln. This type of die is well known in the art and is used ordinarily in the production of dry, semidry and wet processed porcelain. The forming press, furthermore, should be one capable of exerting upon each charge in the die a compression force of not less than one and one-half tons per square inch and upwards to at least five tons per square inch. It may be desirable in some instances to exceed that pressure and even to exert a pressure as high as ten tons per square inch upon the charge in the die. Hydraulic presses capable of exerting such pressure are available on the market.

Because of the dry character of the material employed and the density imparted to it by the tremendous pressure under which the articles are formed, each article as it is pushed out of the die by the following charge of material is of S c stiffness and compactness that it is self-sustaining before firing or drying, as distinguished from the somewhat limp and flexible articles formed by the usual extrusion method. The articles dieformed by my method could, because of their compactness and rigidity be handled by hand without the necessity of employing pallets. No manual handling, however, is necessary, since the travel of the material throughout my entire process is accomplished by carriers which automatically advance the material and formed articles from point to point in their progress toward completion.

Upon leaving the forming press, the compressed article may or may not be sprinkled with sand or other surfacing material with or without color. If such treatment is desired, it can be performed at this point by an apparatus, indicated by reference character 5, which is well known in the art and which sprinkles the surface of the article as it travels therebeneath with such granular material as will produce the surface desired on the finished article. In the production of many articles, however, this step is omitted entirely.

The formed article after being ejected from the die is next conducted by a suitable conveyor to the drier 6, the structure of which is well known in the art, and Where the formed and compacted articles are subjected to a drying operation as they pass through the drier. Any suitable means of heating the drier may be utilized, although for purposes of economy it is customary to utilize waste heat from the firing kiln.

By reason of the low moisture content of the articles, the drying time may be reduced from twenty-four hours, customarily required, to approximately one hour. The length of the drier, therefore, and the speed of the conveyor by which the articles are progressively advanced through the drier are so co-related that the articles will be subjected to the drying temperature of approximately 300 F. or less for just about one hours time, when they will emerge from the drier or drier section of the continuous kiln on a conveyor and enter in succession into the tunnel kiln indicated on the drawing by reference character 1. The time and consequently length of the drier are regulated by both the desired production and character of the material being used.

The progress of the articles through the tunnel kiln is also continuous, consequently, the length of the tunnel is so related to the speed of the carrier or endless conveyor upon which the articles are supported that the articles will remain in the tunnel kiln (where a temperature not exceeding 2000 F. is maintained and which preferably is between 1400 and 1800 F.) for a relatively short period as compared with the firing time under present customary methods. By reason of the dryness of the articles as they enter the kiln and their compactness resulting from their die formation, a firing time of not more than three hours is, under normal conditions, sufficient to thoroughly fire and produce an excellent product. In some instances, depending somewhat upon the size of the articles, considerably less time than three hours is required, and in exceptional instances somewhat more may be necessary, although in no instance have I encountered a firing requirement of as high as five hours.

The importance of thus firing in approximately three hours will be appreciated when it is recalled that by former methods of production,

when a continuous tunnel kiln is employed, a minimum of sixty hours is required for firing, and when periodic kilns were used a three weeks firing cycle was a necessity. Furthermore, in previous processes the temperature range was between 1850 F. to 2300 F., whereas, with my method the maximum firing temperature is only 1800 F.

As the articles are discharged from the tunnel kiln I after three hours firing, they are delivered by a conveyor 8 to a point where, when sufficient- 1y cool, they may be loaded for shipment.

One form of finished ceramic product illustrated as a roofing tile of the Spanish type is shown in Fig. 8. My method, however, is equally suitable for the production of Mission tile, clay shingles, or any other desired shape of ceramic product.

It will be apparent from the foregoing that my novel method is carried out automatically, without manual handling of the product, from the time the raw material enters the chargemeasuring and feeding apparatus until the finished product is removed from the final conveyor. All of the conveying apparatus by which the raw material and the partially and completely formed products are advanced operate in timed relation with each other and with the apparatuses employed in the method. The articles formed by the forming press are conducted through the dryin and firing apparatus so that all of the articles are at the same height and in the same relative relation to the source of drying heat and of firing heat, thereby insuring a similar treatment of all of the articles and the final production of a product of uniform character, both as to structural characteristics and appearance.

It will also be obvious that the time consumed in the making of a batch of products is reduced from weeks when periodic kilns are employed or days when tunnel kilns are employed, to a matter of a very few hours. My method also results in an enormous saving in heat energy by reason of the fact that no extended drying period is involved and, furthermore, because of the very small amount of water required to be driven off during the firing cycle which greatly reduces the amount of heat required in the actual firing of the pieces. The economy of this method as compared with those heretofore practiced is at once manifest.

Furthermore, the product itself, because of its compactness, is stronger both as to its modulus of rupture and as to its crushing strength than products of the same type produced with the ordinary method, and in addition its capacity for absorption is reduced approximatel twenty-five percent from an average of eleven percent to an average of eight percent.

While I have illustrated and described in detail the preferred method of carrying my invention into effect, it should be apparent that modifications and variations in the steps exemplified herein may be resorted to without departing from the essence of my invention as defined in the following claims.

I claim:

1. The method of making ceramic products by a continuous process, which consists in feeding in succession measured charges of relatively dry raw ceramic material such as clay, shale or the like, containing not more than five percent of moisture, shaping and compressing said charges under at least one and one-half tons per square inch pressure into rigid, self-sustaining articles, advancing said thus formed articles in succession, and subjecting the advancin articles to a drying temperature of approximately 350 F. for approximately one hours time and to a subsequent firing temperature between l400 and 2000 F. for approximately three hours time.

2. A vitrified ceramic product of high density having a maximum absorption capacity of approximately eight per cent, a rupture modulus of approximatel 1200 pounds per square inch, and a crushing strength of approximately 2500 pounds per square inch.

3. A vitrified ceramic product compacted to a density precluding an absorption of more than eight per cent by moisture and having a modulus of rupture of 1200 pounds per square inch.

4. A vitrified ceramic product compacted to a density precluding an absorption of more than eight per cent by weight of moisture and having a crushing strength of approximately 2500 pounds per square inch.

5. A vitrified ceramic product having a rupture modulus of approximately 1200 pounds per square inch and a crushing strength of approximately 2500 pounds per square inch.

6. A vitrified ceramic product consisting of compressed clay, shale or the like, possessing not more than five percent of moisture and having a rupture modulus of more than 1500 pounds per square inch and a crushing strength of more than 3000 pounds per square inch.

RUSSELL P. DUNMIRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 445,939 Monk Feb. 3, 1891 1,374,493 Dimitri et al Apr. 12, 1921 2,310,578 Fessler et al Feb. 9, 1943 2,388,679 Davis Nov. 13, 1945 

